Re: January 2010 Yellowstone Seismicity Summary

January 2010 Yellowstone Seismicity Summary

During the month of January 2010, Yellowstone National Park seismicity was dominated by a large swarm of earthquakes in the northwest side of the park that started January 17, 2010. These shocks were located about 10 miles to the southeast of West Yellowstone, MT and 10 miles to the northwest of Old Faithful, WY. As of Feb. 1, 2010, 1620 earthquakes have occurred in the swarm and were located by the University of Utah Seismograph Station (UUSS) automatic earthquake system. The swarm includes 12 events of M3+; 119 of M2.0-2.9; 992 of M1.0-1.9; and 497 of M0.0-0.9. The largest of these shocks was a magnitude 3.8 on January 21, 2010 at 11:16 PM MST. There have been multiple reports of persons experiencing ground shaking from observers inside the Park and in surrounding areas for the larger events.

Earthquake swarms are relatively common in Yellowstone but this is one of the largest in total number of earthquakes. Yellowstone Volcano Observatory scientists consider that the swarm events are likely the result of slip on pre-existing faults and are not thought to be caused by underground movement of magma. Currently there is no indication of premonitory volcanic or hydrothermal activity, but ongoing observations and analyses will continue to evaluate these different sources.

Analysis of the swarm events is an ongoing process and UUSS analysts will continue to review the earthquake data. For additional information please see http://volcanoes.usgs.gov/yvo/publications/2010/10swarm.php

Ground Deformation Summary: Continuous GPS data show that uplift of the Yellowstone Caldera has slowed significantly. Uplift rates for YVO GPS stations are less than 2.5 cm per year. The WLWY station, located in the northeastern part of the caldera, underwent a total of ~23 cm of uplift between mid-2004 and mid-2009. Its record can be found at:
http://pboweb.unavco.org/shared/scripts/stations/?checkkey=WLWY&sec=timeseries_plots&timeseries=raw

The general uplift and subsidence of the Yellowstone caldera is of scientific importance and will continue to be monitored closely by YVO staff.

An article on the recent uplift episode at Yellowstone and discussion of long-term ground deformation at Yellowstone and elsewhere can be found at: http://volcanoes.usgs.gov/yvo/publications/2007/upsanddowns.php